Update:1999.4.21

KEKB accelerator is being commissioned steadily. On March 9, the beta-value at the interaction point (this value is a measure of the degree of beam) in the low-energy positron ring (LER) was squeezed from 2 cm to the designed value of 1 cm. The injection to and the beam storage in LER were not affected by this change; the maximum stored beam current in LER had increased from 240 mA to 370 mA within a weak. Following LER, the beta-value at the interaction point in the high-energy electron ring (HER) was changed from 2 cm to 1 cm on March 21. These beta-values are the world smallest value among existing electron-positron colliders..

On March 26, beam collision between multi-bunch (200 bunches) 65-mA positron beam and 13-mA electron beam was tried. The luminosity calculated from the beam-beam kick data was 1.7 x 1031cm-2s-1 (see Figure).

After this trial of collision, effort was concentrated on the increase of the stored current in HER and LER; the maximum stored currents are now 514 mA in HER and 532 mA in LER.

Figure 1: Increase of the stored currents in HER and LER from the start of the commissioning in December 1998 to early April 1999. The bottom graph shows the accumulation of integrated currents.

Figure 2: Increase of the stored currents in HER and LER from the start of the commissioning in December 1998 to early April 1999. The bottom graph shows the accumulation of integrated currents.

	[Related URL]
	KEKB Accelerator
	KEK HOME